Until the late 1940s, the concept of cybernetics had not distinguished control
and communication as separate fields. It is only after Shannon's revolution
that
communication and information theory branched out of system theory. Recently,
however, decentralized control systems (where multiple controllers explicitly
and implicitly communicate with each other) are demanding for the
reunification
of control and communication theory. In this talk, we will attempt this
unification by revealing information flows for control. More explicitly, we
will
consider the simplest decentralized LQG problem, an infinite horizon average
cost scalar system with two controllers, and find a surprising parallelism
between decentralized control and wireless communication theory.